The present invention pertains to a thread guide rail for crochet galloon machines.
It is known that crochet galloon machines consist of a number of cooperating members adapted to create a fabric. In more detail, a needle bar is provided carrying a plurality of needles directed according to a common horizontal plane. The needle bar, controlled by suitable devices, is provided with a reciprocable movement in the extent direction of the needles which are slidably supported by a needle-row parallel to the needle bar and substantially act so as to interlock the warp yarns with the weft yarns. Warp yarns are fed by eye-pointed needles carried by a guide bar facing the needles and directed parallelly to the needle bar. The eye-pointed needles are operated in synchronism with the needles and according to horizontal and vertical combined movements giving each eye-pointed needle a trajectory extending astride of the corresponding needle. Weft yarns are fed to the needles by threading tubes connected each to a free end of a thread guide element in turn engaged with a thread guide rail. The latter extends parallelly to and above the needle bar, so that it exhibits the threading tubes in the region of the needles themselves. Furthermore, the thread guide rail is subjected to horizontal and vertical combined movements giving each threading tube a trajectory extending astride of a corresponding needle, similarly to what said about the eye-pointed needles.
The object of the present invention is to provide a new type of thread guide rail as those currently used have proved not to be quite suitable to operate at the high operating speeds required by modern crochet galloon machines.
In this connection it is to be noted that thread guide rails currently used exhibit a substantially rectangular section on the major base of which is located an upwardly inclined flat provided with a groove extending longitudinally to the rail itself. The face opposite that having the inclined flat is provided with a series of transverse grooves disposed side by side and extending transversely to the thread guide rail over the whole width thereof.
Each thread guide element is rigidly engageable to the thread guide rail in the region of a U-shaped elastic portion thereof which, by forced fitting, can be located over and on either side of the rail itself and which exhibits a fitting projection snap-entering the longitudinal groove.
In addition, each thread guide element exhibits, after the elastic U-shaped portion, a rectilinear portion carrying a tube at its free end and housed, over a short length thereof, along one of the transverse grooves against which it is pressed by the spring action of the U-shaped portion.
The drawbacks proper to the thread guide rails of known type consist in that they are not capable of supporting the thread guide elements connected thereto in the best manner when high operating speeds are reached.
In greater detail, the thread guide elements tend to take incorrect positionings relative to the thread guide rail due to the sudden reversals of motion transmitted to the same by the rail itself. In fact the free length of said rectilinear portion, owing to the inertia thereof, is subjected to important deformations and "flag-wavings" during the motion reversals. Furthermore, said flag-wavings often cause the rectilinear portion to disengage from the respective transverse grooves, which results in an undesirable positioning in space of the same.
The disengagement possibility between the rectilinear portion and the respective housing is remarkably increased by the fact that the transverse grooves have a continuous linear extension. As a result, the thrust actions of the rectilinear portions of said thread guide elments, due to the spring actions of the respective U-shaped portions are unevenly distributed all over the transverse grooves; this inconvenience is further increased by the unavoidable structure faults exhibited by the respective contact surfaces.
If most of the action exerted by the U-shaped portion discharges close to the upper end of the thread guide rail, which often occurs, the engagement efficiency between the rectilinear portion and the corresponding transverse groove is remarkably reduced. Practically, the rectilinear portion only engages with a restricted groove length. As a consequence, the length of the rectilinear portion susceptible to deformations due to flag-waving increases and, as a result said deformations become more frequent.
The efficient engagement between the rectilinear portions and the respective transverse grooves is further restricted by the fact that the transverse grooves seen in section exhibit a triangular outline while the rectilinear portions of the thread guide elements exhibit, in the regions of their engagement with said grooves, a substantially rectangular section with rounded edges.
Due to the above discussed drawbacks known rails must be used at relatively low operating speeds, as an accidental disengagement of one single thread guide element from the respective groove would bring about serious complications in the machine operation.